Many developments have been made over the years to motors, in particular to those motors which are used in domestic household appliances. However, it is generally believed that the trend of improvements in relation to universal motors is nearing its end. It is therefore an object of the present invention to provide a motor which is suitable for providing the appropriate power to various parts of a domestic household appliance and which also has scope for improvement beyond the potential of known universal motors.
Domestic household appliances such as vacuum cleaners very often include a universal motor adapted to drive the fan used to create the suction by means of which air is drawn into the vacuum cleaner. When the vacuum cleaner is an upright cleaner, a brush bar is usually mounted rotatably in the dirty air inlet located in the cleaner head. The brush bar is rotated by means of a drive belt extending between the motor and the brush bar. There are many disadvantages of this arrangement, not least of which is the vulnerability of the drive belt itself. Other disadvantages include the fact that, in most cases, the drive belt engages with a portion of the outer surface of the brush bar which means that brush bristles cannot be located in that area. It is also advantageous to have some sort of mechanism for preventing the brush bar from rotating against a carpet to be cleaned if, for any reason, the motor is left running whilst the vacuum cleaner remains stationary, for example, whilst carrying out above-floor cleaning.
In a cylinder cleaner, the dirty air inlet is situated at the end of a hose, hence a drive belt to the main vacuum motor is impractical, and driving the brush bar directly by a secondary universal motor has practical difficulties. Pneumatically powered "turbo" brushes have been proposed, but they are normally inefficient and reduce the power watts available for the pickup of dirt and dust by the cleaner head.
It is therefore an object of the invention to provide a motor suitable for use in a vacuum cleaner having a driven brush bar but which reduces or eliminates the problems identified above.